1. Field of the Invention
The present invention relates to an integrated circuit which can be operated in at least three different organization forms which can be set externally, and has a connection pad which can receive an external signal stipulating one of the organization forms.
Integrated circuits, such as integrated memory circuits, are used in different data configurations or organization forms. The organization forms differ, in particular, in the number of data lines used which are connected to data connection pads, xe2x80x9cI/O padsxe2x80x9d. Upon selection of one of the settable organization forms, a system bus width predetermined by an environment can be set. The data connection pads are used for interchanging data between the integrated circuit and a system controller, for example. There are xe2x80x9cx4xe2x80x9d, xe2x80x9cx8xe2x80x9d and xe2x80x9cx16xe2x80x9d organization forms, which use 4, 8 or 16 data lines per circuit or chip for data interchange.
If the fundamental configuration of an integrated circuit allows it to be used in all of the x4, x8 and x16 organization forms, and accordingly allows the data length for a data bus in the circuit to be configured, it is necessary to set the organization form in question before the integrated circuit is put into operation. For this purpose, a plurality of connection pads are generally provided which can receive external signals or connections for stipulating a respective organization form.
To set the three aforementioned organization forms for an integrated circuit, two connection pads are provided, for example, which receive three different types of connection. This involves the connection pads either having ground potential connected to them, for example, or being left floating. By way of example, the respective organization forms are set by generating respectively different states when the ground potential is connected to a first connection pad, when the ground potential is connected to a second connection pad, and when both connection pads are left floating. Each of the states is significant to an organization form.
In order to provide connection pads on a chip in an integrated circuit, it is necessary to make a certain surface area available on the chip. As the development of integrated circuits progresses to an increasing extent, the aim in this context is to reduce the size of the chip area further. Since the size of the connection area on connection pads cannot be reduced arbitrarily, the increasing reduction in the size of the chip area results in problems in still accommodating the necessary connection pads on the chip.
It is accordingly an object of the invention to provide an integrated circuit having a connection pad for stipulating one of a plurality of organization forms, and a method for operating the circuit that overcome the above-mentioned disadvantages of the prior art devices and methods of this general type, in which the number of connection pads required for stipulating one of a plurality of organization forms for the integrated circuit can be kept as low as possible.
With the foregoing and other objects in view there is provided, in accordance with the invention, an integrated circuit. The circuit contains a connection pad for receiving an external signal for stipulating one of at least three different organization forms for operating the integrated circuit and a control circuit for setting one of the three different organization forms. The control circuit has an input and an output. The input is connected to the connection pad, and the control circuit is able to generate at least three different states at the output to identify a respective organization form, depending on the external signal applied to the connection pad.
The inventive integrated circuit is provided with a control circuit for setting one of the organization forms for the integrated circuit. The control circuit has an input and an output, the input is connected to the connection pad that can be used for stipulating one of the organization forms externally. The control circuit is in a form such that it generates at least three different states at its output to identify the respective organization forms, depending on the signal on the connection pad. Provision of the control circuit allows at least one connection pad to be saved as compared with the embodiment described in the introduction. The invention requires only one connection pad to be provided in order to set at least three different organization forms for the integrated circuit.
In one mode of the integrated circuit, for example after the supply voltage of the integrated circuit has been connected in an initialization mode, the signal state at the output of the control circuit is checked. According to the signal state that is read at the output of the control circuit, one of the organization forms is activated. The control circuit is then disconnected from the voltage supply for the integrated circuits, which achieves a reduction in power consumption.
This advantageously prevents provision of the control circuit from causing additional power consumption in a normal mode of the integrated circuit, for example.
The invention can be used particularly advantageously for an integrated circuit in the form of a memory circuit, for example in the form of a DRAM memory. In line with the invention, it is thus possible to use just one connection pad to set one of the x4, x8 or x16 organization forms.
In one embodiment of the present invention, the control circuit generates respectively different states at the output when a first supply voltage is connected to the connection pad, when a second supply voltage, which is different than the first supply voltage, is connected to the connection pad, and when nothing is connected to the connection pad.
In one development of the control circuit, the control circuit has a first and a second resistor series circuit that are connected in parallel with one another. An output signal at the output of the control circuit is produced by tapping off and comparing a first potential on the first resistor series circuit and a second potential on the second resistor series circuit. The connection pad is connected to one of the resistor series circuits.
In accordance with an added feature of the invention, the first resistor series circuit has a first resistor and a second resistor connected in series. The second resistor series circuit has a third resistor, a fourth resistor and a fifth resistor all connected in series. A first output signal at the output of the control circuit is produced by tapping off and comparing a potential between the first and second resistors and a potential between the third and fourth resistors. A second output signal at the output of the control circuit is produced by tapping off and comparing the potential between the first and second resistors and a potential between the fourth and fifth resistors. The connection pad is connected between the first and second resistors.
In accordance with another feature of the invention, the first and second resistors have different values from one another, and the fourth and fifth resistors in total have essentially a value of the third resistor.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in an integrated circuit having a connection pad for stipulating one of a plurality of organization forms, and a method for operating the circuit, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.